The invention has been developed primarily for the controlled delivery of liquifiable gases or gas mixtures such as CO.sub.2 or CO.sub.2 based preparations, examples of which include CO.sub.2 based pesticide formulations. However, it will be appreciated that the invention may be used to regulate the distribution of many other types of gases, both liquifiable and non-liquifiable.
Gaseous pesticide preparations having a CO.sub.2 base are particularly useful for fumigating grain storage silos. However, numerous problems have been encountered when trying to regulate the distribution of such gas products. One reason is because the product is stored in the liquid state under high pressures of around 5000 kPa and is preferably distributed at a significantly lower pressure of around 10 to 100 kPa.
Operational problems are usually encountered when using conventional pressure regulating devices to distribute gaseous products of this kind, particularly with gases such as CO.sub.2. This is due to the severe pressure and temperature changes that occur when distributing the gas as well as the associated volumetric expansion caused by the resultant gasification of the liquid gas. While the severity of these effects will vary with various gases, they will nonetheless be present in the low pressure distribution of almost any gas from a higher pressure source.
In the prior art, pressure regulation of such preparations was usually achieved via control valves for high flow rate applications and special purpose regulators for lower flow rate installations. However, neither of these devices are generally able to maintain an even pressure when regulating liquified gases to a gaseous state. In such cases dry ice tends to form at the valve seat causing "spitting" and the output tends to fluctuate wildly due to the large increase in the volume of the gas and the irregularity of the flow. It should also be noted that the use of control valves with the necessary associated control equipment is a relatively high cost option.
Furthermore, as these various prior art regulating devices are usually designed to operate in-line, the components of the device are subjected directly to variations in temperature and volumetric changes referred to above, and as such may have a reduced life span.
Another problem associated with the regulation and delivery of preparations such as CO.sub.2 based pesticides, is the gradual build-up of resin-like polymer residues which adversely affect the operation of the prior art regulation devices.
It should also be noted that regulators used in fumigant delivery systems for dispensing gaseous pesticides of this kind are often required to operate continuously without monitoring for periods of time on the order of 30 days. Accordingly, safety, reliability and consistency of operation are extremely important. Furthermore, as there is a large market composed of small farming operations, there is a need for a regulating system that is reliable but not prohibitively expensive.
It is an object of the present invention to provide a gas pressure regulator that overcomes or at least ameliorates one or more of the above discussed disadvantages of the prior art.